In the past, in optical network communication, there has been a super channel in which transmission is performed with sub carriers as one transmission unit. Since performing transmission by using, for example, 4 sub carriers, the super channel uses bands of 4 wavelengths. In a transmission path in which usage rates of bands are high and available free bands are fewer, it becomes difficult for the super channel to secure bands with an increase in the number of sub carriers. Therefore, there is a technology in which a transmission amount is monitored in an optical transmission device on a transmitting side and transmission performance of the optical transmission device is controlled so as to be boosted in a case where the transmission amount exceeds an allowable load of the optical transmission device.
However, in the above-mentioned technology, there is the following problem. In other words, in, for example, a case of setting a new path of a new super channel or a case of setting a new path for troubleshooting an existing path, it is difficult to secure the number of sub carriers to be used by the super channel in a transmission path in which the new path is to be set. This problem will be described with reference to FIG. 13A and FIG. 13B. FIG. 13A and FIG. 13B are diagrams each illustrating an example of an outline of processing for path setting according to a technology of the related art.
FIG. 13A and FIG. 13B illustrate an example in which it is difficult to secure sub carriers of a new super channel according to a new path in a case of setting the new path of the super channel. As illustrated in FIG. 13A, Path #1 is set as an existing path in a transmission path between a node A and a node Z, and Path #2 is set as an existing path in a transmission path between a node B and the node Z. At this time, Path #3 is to be set as a new path in a transmission path between a node C and the node Z.
However, as illustrated in FIG. 13B, even if Path #3 is intended to be set in the transmission path routed through a section between the node A and the node Z, Path #1 uses a sub carrier of a wavelength λ3. Therefore, it is difficult for Path #3 to use the sub carrier of the wavelength λ3 in the transmission path routed through the section between the node A and the node Z, and as a result, it is difficult to set Path #3 in the transmission path routed through the section between the node A and the node Z. In the same way, even if Path #3 is intended to be set in the transmission path routed through a section between the node B and the node Z, Path #2 uses a sub carrier of a wavelength λ1 and a sub carrier of a wavelength λ2. Therefore, it is difficult for Path #3 to use the sub carrier of the wavelength λ1 and the sub carrier of the wavelength λ2 in the transmission path routed through the section between the node B and the node Z, and as a result, it is difficult to set Path #3 in the transmission path routed through the section between the node B and the node Z. In other words, in the above-mentioned technology, it is difficult to flexibly set a path of the super channel.
The followings are reference documents.    [Document 1] Japanese Laid-open Patent Publication No. 2013-207480 and    [Document 2] Japanese Laid-open Patent Publication No. 2008-160227.